The objective of this proposal is to develop improved means for noninvasive diagnosis of venous thrombosis. These will include two major activities. The first is development of a computer controlled cuff for programmed augmentation of pressure and flow in leg veins that will enhance the detectability of Doppler and B-mode signals from the veins, particularly with Doppler flow imaging, and provide additional information about their patency from the induced dynamic response. This enhancement of venous flow will also be applicable to other venous studies, such as MRI, and provide physiologic information about venous dynamics in normal and diseased states that should be useful for the development of new diagnostic, and possibly new therapeutic, methods. The second activity is the development of a novel transducer and associated image reconstruction methods that will interface directly with a commercially available B-scanner and produce images of venous vessels and thrombi with greatly improved resolution of fine scale structural and attenuation characteristics. A concave curved array transducer with a programmable linear array imaging system will be developed in collaboration with a commercial firm. The array will aim and focus ultrasonic beams from many angles onto a small field near the vein, permitting imaging of both structure and attenuation with high resolution, signal-to-noise, and contrast. From this information, the age and stability of a blood clot should be directly interpretable from the image.